


Jealousy

by Acting4Hope



Category: Undertale (Video Game)
Genre: F/F, Mentions of Partial Nudity, Post-Pacifist Route, alcohol mention, mentions of nudity
Language: English
Status: Completed
Published: 2016-02-02
Updated: 2016-02-02
Packaged: 2018-05-17 18:31:11
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,883
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5881204
Author URL: https://archiveofourown.org/users/Acting4Hope/pseuds/Acting4Hope
Summary: <blockquote class="userstuff">
              <p>Undyne was having a bit of trouble with a certain coworker of Alphys's, whom she couldn't seem to stop talking about. With the help of Mettaton, Undyne was able to shut Alphys up about him for good.</p>
            </blockquote>





	Jealousy

**Author's Note:**

> Is this really the first close-to-sin thing I've written and posted here?? Really?? I mean, this is my second attempt at anything close to it, so i hope it's alright! So yeah!! 
> 
> This idea is based off of the song "Genghis Khan" by Miike Snow (really great song. Highly recommend)! If you wanna listen to it while you read here is the song: https://www.youtube.com/watch?v=P_SlAzsXa7E 
> 
> With that all being said, hope you enjoy!!

The liberation of the monsters from the Underground brought a lot of good things to the world. With the added population, more jobs came to fruition, and the prices of certain goods went down. Relations between countries began to settle, once the new Monster Ambassador brought their pacifist ideals to the world leader’s tables. Everyone, monster and human alike, could agree that the integration of both configurations of being was a step for the better. 

 

There was only one person who could beg to differ, and that was Undyne. For you see, she had one issue with the humans; their affinity toward Undyne’s cute lizard girlfriend, Alphys. 

 

Undyne and Alphys had only begun dating once they got to the surface, thanks to Frisk’s and Papyrus’s clever secret date they had set up for the two, and Undyne hadn’t felt any sort of anger toward a person who glanced at Alphys or talked to her. Back then, everything was alright. Plus, Undyne needed to build proper relations with the humans, so she wasn’t going to try fighting any of them over whether they had the right to look at Alphys they way they did. 

 

No, it wasn’t until Alphys had gotten a job at this big science lab that Undyne had started to get a little jealous. Of course, Undyne would never admit to feeling jealousy, but you could see it in her twitching eye and clenched fists. Undyne wasn’t going to tell Alphys about these feelings, also, because Alphys seemed finally accepted by a group of people and was happy about it, even if some of them stared a bit too long at her tail. Just so long as Alphys was happy, Undyne was going to keep her anger at bay. Once Alphys felt the tiniest bit uncomfortable, though, all bets were off for Undyne. 

 

“Undyne?! Undyne are you home?!” Alphys said excitedly as she entered their shared apartment. Undyne lifted her head off the couch and looked at Alphys with a pleasant grin. 

 

“I’m home, babe, what’s up? How was work?” Undyne replied, surprised when Alphys came rushing over to her, planting her face with little kisses. Alphys was never this affectionate and it completely threw Undyne for a loop. Once Alphys calmed down a little, she sat in Undyne’s lap with an evident excitement. 

 

“Work w-was great!! Oh, I had so much fun!!” Alphys started, that familiar spark lighting in her honey brown irises, “I was sent to work in a new division of the lab, w-which I thought was going to suck, b-but it didn’t!! Everyone there is really friendly!! S-Some of them have even read documents about the research I did in the Underground! I spent all of my lunch break telling these scientists about how the Core worked and how I built Mettaton! They were all so fascinated with it, it was a-amazing!!” Undyne was grinning fin-to-fin, her girlfriend’s excitement filling her with a warm feeling inside. Alphys was so passionate with everything she did, whether she knew it or not. It filled Undyne with a warm, fluttery feeling whenever she got like this. It reminded Undyne of how she first fell for the Royal Scientist; how she ended up breaking her phone from squeezing it too hard one night during a call with Alphys who seemed very fired up about the anime they had just watched the day before. She wished Alphys could see what Undyne saw whenever she got fired up; that fiery passion blazing in her eyes, the slight tremble of excitement in her lips and fingers It was all so mesmerizing to Undyne. Every time Undyne sees Alphys like this, she swears she’s fallen in love all over again. 

 

“A-And there’s this guy there who’s really great!! His name is Allen a-and he’s so sweet!!” Alphys finished, drawing Undyne from her thoughts. This type of information was certainly...new. Alphys never really picked people out by name at her work, but for some reason this “Allen” was so important Alphys just  _ had _ to mention him. Undyne contained the bubbles of irritation she was feeling to look at Alphys with arched brows. 

 

“Allen? What’s so special about him?” Undyne asked, feigning nonchalance. Oh, how Undyne wished she hadn’t asked that. For the next  _ half an hour  _ Alphys rambled about all of Allen’s achievements, personal qualities, and past history. It was as if Alphys had known this guy for years, despite knowing him one day. 

 

And it pissed Undyne right the hell off. 

 

The entire time Alphys is rambling, Undyne’s grip on the couch’s arm is getting tighter and tighter, to the point where Undyne feared she was going to break another couch arm and they’d have to buy a new couch. That would be the fourth couch since they’ve gotten this apartment, and Undyne didn’t have the money for another one. Alphys seemed to go on forever about this guy, until eventually Undyne had to fake an important call just to get the conversation to end. She went outside in the hallway to cool down, but all leaving the room did was make her angrier. 

 

“Ugh, what is her deal with that Allen guy?!” Undyne muttered in frustration, running her webbed fingers through her fiery red hair. “It’s like she’s got a crush on this guy!!” That thought alone filled her with enough rage for her to suplex a hundred boulders all at once. If Alphys had a crush on anyone in this entire world, Undyne was praying it was still her. Of course, Alphys was her own monster and was completely free to fall in and out of love with whomever she’d like. But, poor Undyne only had room in her heart for her little nerd, and she would be devastated if Alphys left her for someone else. 

 

It took her a few minutes to calm down, but she did, and then she went back inside. The rest of that night was spent cuddling on the couch watching 90’s anime, and not a word about Allen was spoken. Undyne was content with that. 

 

But the Allen conversations didn’t end after that night. No, there were more, so many  _ more _ . Alphys never stopped talking about him; it was like she had nothing on her mind but Allen. When she came home from work, it was Allen she first talked about. When Undyne called her from work, she immediately was told about what stupid chemical pun Allen made earlier that day. Hell, even on their  _ dates _ Alphys was talking about Allen. The whole situation was just making Undyne increasingly jealous. Whenever she was alone, she was busy punching her frustration out about her girlfriend’s obsession over her coworker. Undyne never talked to anyone about it, though, until one particularly frustrating day. 

 

Alphys was at work, as usual, and Undyne was at the gym getting some reps in. And who just happens to stroll in as well, clad in pink leg warmers and a sweatband? 

 

“Hello, Undyne~!” It was the one and only Mettaton, or, as Undyne liked to call him, Metalhead. 

 

“Hey, Metalhead,” Undyne replied with a grunt as she set the squat bar back on the rack, “What brings you to the gym? Isn’t your body, like, already pre-made like that?” Mettaton made a little clicking noise with his tongue as he strutted over to the weights, picking up the lightest possible one. 

 

“Yes, there really is no purpose for me to go to the gym, it’s true. But, it’s the only place that I could think of where I knew  _ you  _ would be!!” He explained. Undyne cocked her head to the side. 

 

“Me?” She asked, pointing to herself, “Whaddya want with me? We’re not even friends. I don’t even like you.” Mettaton sighed, walking over to Undyne and putting a hand on her shoulder. 

 

“You may not like  _ me _ , darling, but you  _ do  _ like Alphys,” Mettaton replied. Undyne attention was caught at the mention of Alphys. 

 

“...What do you want?” Undyne asked. Mettaton sighed again and pulled out his phone. 

 

“You see, my dear fish friend, I believe me and you are running through a very similar, eh... _ issue _ , let’s just call it, involving our dearest Alphys.” He began as he showed Undyne the screen of his phone. Undyne scanned over the messages. She didn’t even need to look at the contact to see who was talking to Mettaton, based on what the messages were filled of. 

 

“She seems to be, uh, how do I put it,  _ fascinated _ with a particular coworker of his. I believe you know his name,” Mettaton continued, putting his phone back in his pocket. Undyne felt anger boiling inside of her as she turned her attention back to the squat bar, placing all of the weights onto the sides of it. 

 

“Yeah, that  _ Allen _ guy, right?” Undyne said, practically spitting out the man’s name. Mettaton nodded. 

 

“Apparently you and me have the same feelings about this Allen fellow,” Mettaton stated. “Personally, I think the man is trouble. I think he is trying to ruin a perfect relationship that I have tried so hard to get together and keep together. I want him out of Alphys’s life and I want him out of her mind.” Undyne stopped her intense lifting to look at Mettaton. 

 

“Ya know, Metalhead, me and you are finally seeing eye-to-eye, for once.” Undyne replied, setting her squat bar down again. “But what can I do to stop her? She’s happy. I don’t want her to think I don’t want her to be happy just because I hate this guy! She’s gonna think I’m policing who she talks about, then!” Undyne sighed, “And besides, she’s goin’ out for drinks with this bozo tonight, along with her other coworkers. I can’t stop her from talking to him there.” 

 

It appeared, at this time, that Mettaton had an idea in his head. He grinned wickedly, grabbing Undyne by the hand. 

 

“I’ve got some ideas on how to keep her occupied on you, darling~” He said, then he dragged her out of the gym. 

 

Later on that night, Undyne was ready, but unsure. She had everything that Mettaton had gotten for her, but she wondered. 

 

“Damn, I hope this works,” Undyne said as she flopped onto her bed and waited. 

 

Meanwhile, Alphys was having a grand old time with her friends from work. The bar was packed with scientists, who were all celebrating after a huge break in the genetics department. Everyone’s pockets were about to be lined with a bit more dough, so they felt a big party was in order. It was scientists only, so Alphys couldn’t bring Undyne, even though she really wanted to. Undyne was her rock in social situations, and she often looked to her buff girlfriend when she became too overwhelmed. Tonight, to Alphys’ surprise, she was not anxious or overwhelmed. She actually felt normal for once. 

 

“Hey, Alph, I got us some drinks!” Alphys turned at the sound of her friend Allen’s voice. He was making his way through the crowd, two mugs of beer high held high in the air so no one would spill them. Alphys smiled, moving her purse off of the stool she was saving for him, and thanked him once he reached her. He sat down on the stool, taking a large sip of his beer, before turning to Alphys and smiling. 

 

“You doing alright over here? How are you feeling?” Allen asked, well aware of her anxiety and her frequent panic attacks in public spaces. Alphys nodded, taking a small sip of her beer. 

 

“Y-Yeah, I’m good. It’s funny, for once I feel n-normal in public. L-Like I’m just another human living their life…” Alphys explained. She felt her purse vibrate, but ignored it. Allen gave her a gentle pat on the back. 

 

“Hey, you’re a lot more than a  _ human _ !! Humans are boring, there’s like a billion of us around! But  _ you _ , you’re different! You’re your own damn species of life, for Christ’s sake! Do you know how freaking  _ amazing _ that is?! You should be proud to be you; to be Dr. Alphys, former Royal Scientist of the Underground!!” Allen replied, making wide gestures with his free hand that nearly caused a drink to knock out of someone else’s hand. Alphys blushed and looked away, her phone vibrating again. 

 

“Y-You’re such a flatterer, Al,” Alphys said, embarrassed. Allen laughed. 

 

“I mean it, I swear!” Allen assured. Alphys rolled her eyes and ignored the weird little twinkle of fascination in Allen’s eyes as he looked at her. 

 

She knew a few humans were more  _ fascinated  _ in her than most, Allen being the most enamored with her. Alphys had dropped a couple hints that she wasn’t interested, using Undyne as the biggest one, but Allen still seemed determined to sweep her off her feet. Alphys thought he was sweet, but she thought Undyne was sweeter. After all, Undyne was the only one for Alphys, in her mind. Alphys was certain she would never love another like she loves Undyne. But, she liked Allen as a friend, and she didn’t want him to stop treating her so nicely. She found that humans tended to do that once they stop getting what they want. 

 

Her phone vibrated a third time, causing Alphys to yank it out to see what was wrong. They were all from Undyne. 

 

_ Hey babe, how’s ur party?? Havin fun??  _

 

_ I miss you, hun. Please tell me how it’s goin  _

 

_ Oh, you’re gonna ignore me, eh? I see how it is.  _

 

Alphys sighed, texting back a quick reply to Undyne before putting her phone back in her pocket. Allen looked at her, his head tilted in confusion. 

 

“Who was that?” He asked. Alphys took another sip of her beer. 

 

“Just Undyne,” She said once she set her beer back down, “She tends to get lonely when I’m out, and so she texts me and asks me how I’m doing. She’s a little impatient, though, so I usually have to reply back quickly.” Allen rolled his eyes, running his finger along the top of his glass. 

 

“She sounds needy to me,” Allen replied, “I don’t think you need to be dealing with desperate girlfriends right now, Alph. She’s going to drag your work down! If I were you, I’d leave her for someone more in my...interest field. Someone you’re going to see a whole lot more.” Alphys laughed, playfully punching Allen in the shoulder. 

 

“Like  _ I _ can find anyone as amazing as  _ her _ on this Earth!” Alphys retorted. Allen let out a short, obviously fake, laugh in reply. “No seriously, Undyne’s perfect. She’s sweet, kind, funny, super passionate, energetic, loving, cute, hot….r-really really  _ hot _ .” Alphys began to sweat, images that were certainly not appropriate for the work area flashing through her head. “God she’s so  _ hot _ .” 

 

Her purse buzzed. Both Alphys and Allen looked down at it, then back up to each other. Alphys chuckled nervously and Allen got the gist of what her look was telling her; it was Undyne texting her and she needed to check it. Allen got up with his drink in his hand. 

 

“I’m going to go see if Paulette and Nikola got smashed yet,” He said, “You have fun with your needy girlfriend.” He sounded irritated, but Alphys knew he was just going to come back later just as happy as he was before. He bounced back like that a lot. 

 

With Allen gone, Alphys turned her attention to her phone. 

 

_ That Allen guy with you?   _

__   
__   
Alphys rolled her eyes, typing back a reply. 

 

**He was before, but I’m alone rn. Why?**

 

There wasn’t an immediate response, so Alphys set her phone down to scan the bar. Everyone was happy, talking and laughing and smiling. It made Alphys happy to see everyone so happy. Her phone vibrated, making Alphys flip it back over to check her messages. She unlocked her phone and waited for the message to load. 

 

And boy, when it was loaded, was Alphys  _ floored _ . If Alphys was drinking her beer, she would have choked on it. She nearly dropped her phone in shock once she saw it. 

 

The message was a picture of Undyne on their shared bed. Her hair looked disheveled, spread out on the pillows, and her eyepatch was off, showing off her permanently closed eye. She was wearing light makeup, the most being the shimmering red lipstick she had on. She was wearing nothing but matching lacy pale yellow panties and a bra. 

 

Alphys was practically drooling over the photo. Her face was as red as a tomato and sweat was beading down her forehead. There was another message written after the picture. 

 

_ Babe, I miss you~ Come home~  _

 

Alphys’s hands shook violently as she typed a reply. 

 

**Jesus fucking Christ Undyne I would if I could, but I promised Allen I’d hang out with him.**

 

Not even half a minute went by and Alphys could already see the notification that Undyne was typing. The message popped up two seconds later. 

 

Undyne was still in her lingerie….minus the bra. 

 

_ You know, babe, it really shocks me that you can still talk abt Allen while I’m dressed like this.  _

 

If Alphys could melt, she would be a pool on the ground by now. Her body, especially her lower areas, were tingling with this red hot feeling that was just getting worse and worse. She tried to drink her beer, in some vain attempt to lessen her trembling, but she just ended up getting half of it on her face and the table. She looked back to her phone, feeling incredibly tempted to just get up and leave. She looked around her surroundings real quick and, once she saw she was basically invisible to the whole bar, she got off her stool and headed for the door. She fumbled with her phone as she texted a reply. 

 

**Hold on Christ pls hold tf on I will be there in two seconds Jesus Christ why do you do this to me why are you so hot**

 

Just as she sent that jumbled mess of a text with absolutely no punctuation, Allen blocked her way. Not intentionally it seemed, but it still startled Alphys. She squeaked, jumping back away from Allen. Allen turned around and looked at her, smiling when he saw it was her. 

 

“Alph, there you are! I was just about to go looking for you!” Allen announced, pausing to inspect Alphys. She looked like a nervous wreck right now, though the kinds of nerves Alphys was currently feeling were certainly  _ not  _ the anxious ones, and she was sweating a lot. “Alph, you doing okay? Is something wrong?” Alphys sputtered and stammered until words were finally able to come out of her mouth. 

 

“N-N-No!! I’m f-fine!! Absolutely p-peachy!! I-I just n-need to go! Home! Yeah! I-I really n-need to go home!! Like right now! At this very moment!” Alphys explained as she tried to scoot past him. But Allen wasn’t letting her get away, not right now. He stepped in front of Alphys and stared her down. 

 

“Is this about Undyne?” He asked harshly, “Did she say something that made you such a wreck like this?” Oh, if only Allen could know what kind of things Undyne was doing to Alphys’ head right now, but she wasn’t going to admit those things in public! So, she just laughed it off and continued to try and slip past him. Allen grabbed Alphys by the shoulders to stop her. 

 

“A-Allen, it’s fine! I-I’m fine!” Alphys said, wriggling to get free. “I-I just want to g-go home, okay?!” Allen sighed and let go. 

 

“Fine, if you want to leave on your own terms, then you can go.” Allen said, much to Alphys’s relief and delight. “BUT! You have to let me drive you home. I mean, I drove you here, so it’s only fair that I drive you back.” Alphys sighed and nodded, walking out with Allen to his car. 

 

The whole car ride was spent in silence, but Alphys was sure to send Undyne a quick text that she was going to be home soon. 

 

Undyne responded with nothing. Nothing on  _ her _ , at least. 

 

When Allen parked in front of Alphys’s apartment, she didn’t even say goodbye. She practically flew out the door and into the apartment. Allen watched her go in, leaning back against the seat once Alphys was out of sight. He closed his eyes, taking in a deep breath, before he heard a knock on the window. He jumped and whipped his head around to the window. He noticed a robotic-looking person with black hair by his window. He rolled it down and eyed the robot curiously. 

 

“Can I...help you?” Allen asked, the robot grinning. 

 

“Why yes, darling, you can~” The robot cooed. “You see, I happened to notice you taking an interest in a little scientist friend of mine. Goes by the name ‘Alphys’?” Allen blushed, laughing nervously. 

 

“Hehe, is it obvious?” Allen asked with a laugh. “Y-Yeah, I like her…” The robot laughed. 

 

“I figured. Now, you do know that Alphys is in a very happy relationship with Undyne, right?” The robot asked, their grin turning the slightest bit into a smirk. Allen nodded slowly, the robot clapping their hands together. “Oh good! You’re not as much of an imbecile as I thought you were~!” Allen was taken aback by the robot’s statement. 

 

“Excuse me-” Allen was cut off by the robot lifting its hand up, signaling silence. Allen didn’t know why he shut up, but he did. The robot continued to smile as they pointed to Alphys’s apartment complex. 

 

“Now you see, I’m going to blunt. The real reason why Alphys left the bar is because I taught her girlfriend the masterful art of taking nudes, and now they’re probably in there having the time of their lives!” The robot stated. Allen almost didn’t process the statement until it nearly flew over his head. Once he did process it, he choked on air. He had no words, but it seemed the robot still did, for they leaned into the car window so they were nose-to-nose with Allen. 

 

“So, I want you to drive off and never  _ ever  _ mess with this perfect relationship that I worked so hard to build, okay?” 

 

Allen drove off as soon as the robot’s head was out of the window. 

 

The next morning, Undyne woke up in a haze. She looked down at the tangled mess of bed sheets, making sure everything that happened last night wasn’t a complete dream. But, with Alphys’s little body curled up next to hers, Undyne knew this wasn’t a dream. She reached over to her nightstand and grabbed her phone. She took a quick picture of her snoozing girlfriend and sent it to Mettaton. 

 

_ Mission success. Couldn’t have done this one without ya, Metalhead.  _

 

**_Anything to see my favorite people be happy together! Oh, and don’t worry about little Allen, I took care of that problem!_ **

 

Undyne smiled and put her phone back down. She ran her hands down Alphys’s back as sleep slowly took her again. 

 

So, now I guess Undyne has no qualms with the humans, right?  

 

KNOCK KNOCK KNOCK 

  
  
“DELIVERY FOR A MISS UNDYNE!” 

 

Well, not exactly.    
  



End file.
